Vehicles having hybrid drives are being developed to an increasing extent; in these vehicles, various drives are used for a drive task. The individual motors in the hybrid drive may cooperate in different ways. Either they act simultaneously or only one drive unit acts on the vehicle to be moved.
With so-called parallel hybrids, an electrical drive is positioned on the shaft of an internal combustion engine. To ensure strictly electrical operation with the internal combustion engine at standstill, the electrical drive is decoupled from the internal combustion engine by a separating clutch. In the event of defects in the separating clutch or in the hydraulic triggering of the separating clutch, the transferrable torque may be much lower than the maximum torque usually available. The torque of the internal combustion engine is used not only for the vehicle drive but also for generator operation of the electric motor, which charges an energy storage device.
In the event of a defect in the separating clutch, the energy storage device is charged further in the usual manner, which may result in torque no longer being available to propel the vehicle. This means that the vehicle is no longer able to move in this case.
It is believed to be understood that in the case of a vehicle having a hybrid drive, the distance the hybrid vehicle is still able to travel is determined after it has been discovered that one drive unit of the hybrid drive is no longer available and it will be necessary to continue driving with the remaining drive unit, which is still functional.